Tube/Solid State Bi-Amplification

I've read about people bi-amping using solid state for lows and tube amps for mids and highs. How is this practically done? I have bi-amp capable speakers but I only have one input on my preamp. What additional equipment would I need to buy and is it readily available? Not to mention, are the results worth all this effort? Has anyone done this??
It depends on your speaker and amps which will determine whether or not it is worth the expense. Your preamp I gather has only one preamp active output rather than the input you mention. You will first need a Y cable to split the signal to each amp. You then run a pair of cables to each amp. This is if each amp has the same gain. If they do not then you would get an unbalanced sound of top and low end. To balance these levels you will need an active crossover that lets you increase or decrease both or one of the two - like the Bryston 10. You could also use 2 peavey Cozmos units (250) each - this will allow volume adjustments of each amp. After you determine this a pair of speaker cables needs to be run from each amp to the proper terminals on the back of the speaker. You need to remove the jumpers that usually connect the two sets of terminals on each speaker . If the you did not use another device such as the crossover than you are set and are relying on the crossovers built into the speakers. This is also true if you used the Cozmos. If you used the Bryston Crossover you may have to disconnect the built in crossover to get a better situation. Some speakers have a switch on the back for biamping instead of removing jumpers. I like the results I get with my Mcintosh 352 (SS) and 2102 (tubes) amps and the VMPS RM 40's. I use the two Cozmos devices with great success. My preamp - the Mcintosh C42 has mutiple outputs so no Y adapter is needed. If it sounds complicated it can be but breaking it into steps helps - it does tend to get costly.
I also bi-amp, but my speakers come with an active outboard crossover splitting the bass and treble signal at about 200hz (it's a 4-piece system). The only things I'd like to add to Ljgj's fine post are that (1) the input sensitivity of the different amps will also play a role in how loud they are vis-a-vis each other--you'll really need a way to adjust the volume of the two amps, whether through an active crossover or perhaps some passive attenuators like EVS makes; and (2) depending on the crossover frequency, the sonic character of the amps you are using can make a difference (I have switched bass amps recently because the new ones are a little faster and leaner in the 200hz region, making for a better transition to my tubed amps on the top; I might not be so concerned were the crossover at, say, 50-60hz); you'd like to get amps that make the crossover sound as seamless as possible. It can be difficult and may wind up costly to do the biamping; I don't think I'd have done it were my speakers not set up for it.

Ljgi has summed up the situation well. I'd like to clarify one point, though. If you use an active crossover (like the Bryston 10B), you'll only need a single preamp output. You'll connect your preamp to the active crossover and then connect the crossover to your power amps. This is called active bi-amping.

You can also connect your pre to multiple power amps and then connect the amps to the speakers. This is called passive bi-amping. In this case you'll need multiple preamp outputs or Y-cables.
Biamp capable speakers usually means there is a high pass filter behind the mid/tweeter speaker input and a low pass filter behind the mid/woofer speaker input. Adding an electronic crossover will mean that you have both active and passive crossover components operating together. -- I use a theme and variation of the tube/solid state approach with a tube amp running two-way floorstanders (bi-wired) and a solid state running a sub. The floorstanders are run full spectrum while the sub amp has an active low pass filter as well as volume and phase control.
The posts above give a good overview of what you'll need to do. Since some experimentation is now needed, it might be easiest to start with a Y-splitter for your preamp's output, then borrow some amps to try out a few combinations of passive biamping. The amps should have roughly the same gain/sensitivity but don't need to match exactly for these initial estimates of blending two "sonic personalities". In your case this approach is probably preferable to an active crossover, since it appears that your speakers already have internal filters (low or high pass) which allow each section to be driven by a full-range amp. But as mentioned above, you eventually might have issues with differing gain unless you introduce passive attenuation in the signal path.
I have been biamping Magnepan MG3.6/R speakers for a couple of years, and have owned or tried a number of amps trying to get the sound I want. I necessarily use an active crossover (Marchand, with level controls, xover at 250Hz, 24dB slopes). Tried many SS+SS combinations (even these can be tough to match sonically!). And I wasn't really satisfied with SS+tube for this speaker, although some people report success (search Planar Speaker Asylum). I ended up with a Llano Design Trinity hybrid amp (tube gain; transistor output) for the mids/highs on the MG3.6. The Llano gives me a tube sound but tends to blend well with my bass SS amp. I've now decided to get another Trinity amp for the bass, and fine-tune the character of each amp via its flexible tube acceptance (e.g. warm 12AX7 for the top and tight-bass 12AT7 for the bottom).
I'll agree that all of the above posts make good points. I have a pair of Magnepan 3.6s that I use with an active crossover. Fortunately, Magenpan provides you with the crossover points and slopes required in the active crossover. If you do not know what freq points/slopes you require, it could be tough to get it right. I chose the Marchand XM126 tube crossover. Mainly because it could be set up for the 18db 250hz low pass and 6db 200hz high pass crossover points. As for the results, having my CA-400 (SS) connected directly to the bass panels provided a more solid (controlled?) bass. I use a Cary SLA 70 (tube) for the top end. The top end really opened up for me and became even more detailed. Vocals were always great, I didn't notice as dramatic an improvent. Going active is a major step, be prepaired to fine tune for a while. It took over a month for me to get everything dialed in perfectly. It's almost like starting over, but the end result payed off.
The above posts are well stated. I would just add that Richard Vandersteen does not recommend "horizontal bi-amping" with his speakers. He claims that it is too difficult to properly integrate the bass with the upper frequencies. Vandersteen does recommend passive VERTICAL bi-amping though. Good Luck. Craig
Thanks to everyone for generously volunteering your experience and expertise. You've really helped clarify this issue for me.